The KC-135
is a modified Boeing 707 four-engine turbojet that NASA uses
to simulate conditions of weightlessness. In a typical flight,
it traverses the Gulf of Mexico in a series of large parabolic
arcs. Peaking at 32,000 feet, the plane then dives to 24,000
feet, its fuselage pitched down at 40 degrees. At the top of
each parabola, passengers lose all sense of gravity and become
weightless for a period of roughly 25 seconds. When the
airplane comes out of the dive and begins its next ascent, the
plane pitches upward at about 50 degrees and passengers on the
craft are subjected to forces up to 1.8 times that of gravity.
This climbing and diving is repeated thirty times in what
might be described as the ultimate roller coaster ride.
Flying on the KC-135 nauseates passengers so frequently,
however, that the plane has been nicknamed the "Vomit
Comet".

Although
best known for its role in astronaut training, about 80
percent of the plane's flights are actually conducted in
support of research or engineering. Under a program
administered by the Texas Space Grant Consortium,
the space agency makes the KC-135 available to undergraduate
researchers for two weeks each year. In March of 2000 I
traveled to the Johnson Space Center in Houston, where my
project team conducted a series of microgravity experiments on
board the KC-135. Our project involved the use of virtual
reality (VR) as a pre-flight adaptation training tool. Our
hope was that advance training in VR would reduce feelings of
motion sickness and give trainees a more intuitive
understanding of the conditions of zero gravity.

Kate trains in the VR simulator.

A screenshot from the simulator showing the
interior of the KC-135 main cabin.

Using Alice,
I programmed a VR trainer that simulated the conditions on
board the KC-135. We theorized that after someone has
practiced a series of simple tasks in the simulator, they
would perform the same tasks more effectively in actual
practice.

Unfortunately, the sample size in our experiment was too
small for the results to be conclusive, but we learned a great
deal about the conditions on the plane. We were able to
modify the simulator to mirror the conditions more closely, so
perhaps it can be used in a future experiment with a larger test
group.

I float weightless on the KC-135.

Want
to see me fly in zero gravity? Here's a video
of Kate, Randy, and I in flight (9 MB).